November 6, 2000
Genetics and Heredity
Question from Newark, Ohio, USA:
Our four year old who was diagnosed with type 1 diabetes eight months ago, and our seven year old was diagnosed with it a month later. Our third child, a nine year old, has had symptoms and high sugar readings. We believe he will be diagnosed as soon as he sees the doctor. There is no known family history of the disease. We are shocked and find it unbelievable that all three of our children have come down with this disease in a nine month period. What are the chances of this? Do you have any other cases or research that would be beneficial to us in finding some answers?
In a situation where neither parent has type�1A (autoimmune) diabetes, the average incidence of the disorder in the first child, in North America, would be roughly 4:1000 by age 18 in Caucasian families. For subsequent children, the risk would be about 5%, all of which adds up to a chance of about 1:100,000 that all three siblings in a family would be involved.
Quite a lot of genetic typing is being done to try to define risk more clearly, but the imponderable is still that of not knowing exactly what the environmental trigger is. The fact that all your children were affected in the same year does not mean that this environmental factor was only present at that time. It would have been necessary to have followed antibody levels from infancy to be sure of that. There is also a national study called DAISY (Diabetes and AutoImmune Syndromes in Youth) that should shed some light on this whole issue, but not for a year or two.